AS/NZS 4777.2 – Inverter Requirements standard
Background
The rapid pace at which Distributed Energy Resources (DER) are being installed is resulting in significant amounts of decentralised generation entering the power grid. At the moment, household rooftop solar, or distributed solar photovoltaics ( DPV) is the dominant form of DER. With well over 2 million DPV systems installed this level of penetration brings opportunities for consumers to access new products and services, and a need to ensure that the power system and all these installations can operate together.
AEMO’s role as the market operator is to ensure a secure and reliable energy supply to all Australians regardless of whether they have DER installed or not. Through the uplift of key standards, and in conjunction with work being undertaken on a two-sided marketplace, we can open opportunities for participation in the energy market.
What is AS/NZS 4777.2
DPV systems are connected to the electricity grid via inverters. Inverters manage how the DPV attached to them interact with the power grid and define how these resources must perform under different system conditions.
AS/NZS 4777.2 specifies the expected performance and behaviour of inverters at low voltages (such as households or small-scale commercial) and the necessary tests for compliance. The recently published uplifted AS/NZS 4777.2:2020 delivers new performance capabilities and requirements that are in-line with international best practice to support secure power system operation with high levels of DER penetration.
What does AS/NZS 4777.2:2020 deliver?
In June 2019, AEMO initiated a review into the Australian Standard AS/NZS 4777.2:2015 after identifying a number of power system security risks resulting from increasing DPV penetration and insufficient capabilities in the existing standard. The revised standard published in December 2020 will deliver the following capabilities essential to operating the grid with increasing levels of DPV generation:
- Improved specificity regarding conditions in which inverters should stay connected and generating power to the electricity grid or disconnect to support power system security and prevent major events.
- Optimisation and coordination of parameters to maximise the value of the capabilities offered with ‘smart’ inverters to provide improved power quality to customers and grid support functions for networks, allowing increased hosting capacity of DER on distribution feeders and in-turn allowing more customers to install DER.
- Improved accuracy and stability of measurement systems used in inverters, to improve the reliability of performance characteristics providing guaranteed responses to different conditions.
- Improved and new testing procedures to ensure enhanced device level compliance is met.
- Making it clearer this standard, as it always did, applies to EV’s when exporting to the grid.
The changes bring this standard inline with international best practice and applies, where possible, similar performance capabilities as large-scale generation. This is because when you add all these small generators together they become the largest generator in the NEM, and so need to be able to deliver similar capabilities to the utility fleet to help keep the system in balance.
The AS/NZS4777.2:2020 Standard can be accessed through:
Inverter inspections
AEMO has been collaborating with the Clean Energy Regulator (CER) and the Clean Energy Council (CEC) to incorporate inverter settings checks into the CER’s existing inspection program as part of its Small-scale Renewable Energy Scheme.
It was identified that as much as 40% of grid-connected inverters installed with rooftop solar PV systems since 2016 may not comply with some of the mandatory settings prescribed in AS/NZS 4777.2:2015 and the relevant Distribution Network Service Provider (DNSP) connection agreements. This is causing issues for grid reliability and security that without rectification will limit consumers’ choice to invest in DER.
The information collected through the inverter settings checks in the CER inspection program will provide insights to better understand reasons for non-compliance to AS/NZS4777.2 and assist in improving processes to minimise this. It will also help inform the standards and testing arrangements that are required in the future, and assist AEMO, the CEC, DNSPs, or state and territory regulators with compliance monitoring.
Compliance with the standards, and ensuring all settings are correct, is essential to increase hosting capacity of rooftop solar PV and other DER on the grid in the coming years, while maintaining grid reliability.
For more information on the Inverter inspections, please visit: